A typical high power, radio frequency (RF) amplifier device may include one or more input leads, one or more output leads, one or more transistors, bondwire arrays coupling the input lead(s) to the transistor(s), and bondwire arrays coupling the transistor(s) to the output lead(s). In some cases, portions of input and output impedance matching circuits may be contained within the same package that contains the device's transistor(s). More specifically, an in-package, input impedance matching circuit may be coupled between a device's input lead and a control terminal (e.g., the gate) of a transistor, and an in-package, output impedance matching circuit may be coupled between a current conducting terminal (e.g., the drain) of a transistor and a device's output lead. Essentially, the in-package impedance matching circuits reduce the magnitude of impedance matching that needs to be performed at the printed circuit board (PCB) level, which is a desirable feature of an RF amplifier device. The above-described bondwire arrays have significant inductive reactance at high frequencies, and such inductances may be factored into the design of input and output impedance matching circuits for a device.
A conventional output impedance matching circuit may include one or more capacitive and inductive elements, where the inductive elements may be in the form of bondwire arrays. For example, an output impedance matching circuit may include a series inductance, which is implemented as a “series” bondwire array that is coupled between the transistor's current conducting terminal (e.g., the drain) and the output lead. In addition, the output impedance matching circuit may include a shunt circuit, which includes a shunt inductance to compensate the output capacitance of the transistor, along with a shunt capacitor coupled in series with the shunt inductance. The shunt inductance is implemented as a “shunt” bondwire array, which in this case is coupled between the transistor's current conducting terminal (e.g., the drain) and the shunt capacitor. Unfortunately, positive mutual inductance between the series bondwire array and the shunt bondwire array may significantly degrade the impedance transformation achievable by an output impedance matching circuit.